1. Field of the Invention
The present invention relates to an improvement in a device for preventing a slide retaining a movable upper die in a tire vulcanizer, particularly of a type such that the movable upper die is vertically moved to be opened and closed relative to a fixed lower die.
2. Discussion of the Background
Generally in a tire vulcanizer, a fixed lower die is fixed on a base of a vulcanizer frame, and a green tire is set on the fixed lower die. Then, a movable upper die is closed and clamped relative to the fixed lower die, and a heating medium such as steam is supplied under pressure to carry out vulcanization and obtain a tire shape corresponding to the shape of the die. A die opening/closing system for opening and closing the movable upper die relative to the fixed lower die is generally classified as a rotary opening/closing system (tilt-back type) including a crank gear, a side link rotatably interlocking with the crank gear and a top link connected to the side link and retaining the movable upper die and a vertical opening/closing system (slide type) wherein the movable upper die is vertically moved along the vulcanizer frame. Such a vertical opening/closing type press is disclosed in Japanese Utility Model Laid-Open Publication No. 58-153025 by the applicant, Japanese Patent Laid-Open Publication Nos. 59-12827 and 61-134210, for example.
In the tire vulcanizer, it is necessary to set the green tire into the lower die under the condition where the movable upper die is opened, and take out the tire after vulcanization from the lower die. During such operation, there is a danger of the upper die dropping or falling from its open position due to a problem occurring or misoperation thereof, and it is therefore necessary to provide a perfect safety measure for preventing such from occurring. From the viewpoint of the above, the rotary opening/closing system as mentioned above is relatively safe since the side link itself is rotated so as to be tilted and retracted upward aside the vulcanizer frame. To the contrary, the vertical opening/closing system has a danger of the upper die falling since the upper die is mounted to a slide vertically movably guided by slide guides provided on the sides of the vulcanizer frame, and the upper die in its open position is located at a upper position on the frame. FIG. 6 shows a conventional falling prevention means for preventing the danger of the upper die falling. Although there have been proposed various mechanisms in the prior art vertical opening/closing type vulcanizer, the mechanism shown in FIG. 6 is an example as disclosed in Japanese Utility Model Laid-Open Publication No. 58-153025 by the applicant. As the details of the mechanism are described in the specification of this prior art, there will be described hereinbelow a falling prevention means for the movable upper die in principal. A vulcanizer frame 1 is constructed of a base frame 1a, side frames 1b and a top platen 1c. A fixed lower die 2 is mounted on the base frame 1a, and a slide 4 is vertically movably guided on slide guides 3 provided on the side frames 1b. A movable upper die 5 is mounted to the slide 4, and a height adjusting mechanism 6 for adjusting the height of the movable upper die 5 is mounted at the center of the upper portion of the slide 4. The height adjusting mechanism 6 includes a rotatable adjusting screw 6a threadedly engaged with a tapped hole 7b formed at a lower end of a hollow pressure member 7 for applying pressure to the movable upper die. The hollow pressure member 7 is in the form of a hollow post, and is formed at its one side with an axially extending slit 7a. Thus, the hollow pressure member 7 is connected with the slide 4. A bracket 8 is fixed on the top platen 1c at a position corresponding to the slit 7a, and a vertically moving member 9 for opening and closing the upper die is mounted to the bracket 8 in concentrical relationship with the hollow pressure member 7. The vertically moving member 9 is constituted of a hydraulic cylinder 9a and a piston rod 8b. The piston rod 8b is connected through a connecting portion 10 to the hollow pressure member 7. Thus, the hollow pressure member 7 is allowed to vertically pass through the top platen 1c, and the movable upper die 5 is adapted to be vertically moved through the height adjusting mechanism 6 and the slide 4, thereby making the movable upper die open and close relative to the fixed lower die. Further, a pressure device 11 is so mounted to the top platen 1c as to surround the hollow pressure member 7. The pressure device 11 is constituted of a hydraulic cylinder 11a and a piston rod 11b. The hydraulic cylinder 11a is fixed to the platen 1c. A stopper mechanism 12 is associated with the piston rod 11b adapted to be moved by supplying pressure into the hydraulic cylinder 11a, and the stopper mechanism 12 is made engageable with the hollow pressure member 7. After the movable upper die 5 is closed relative to the fixed lower die 2, the piston rod 11b is integrally connected through the stopper mechanism 12 to the hollow pressure member 7, and then pressure is supplied to the cylinder 11a to carry out clamping of both the dies. In the vertical opening/closing type tire vulcanizer shown in FIG. 6, the movable upper die 5 is opened by lifting the piston rod 8b of the vertically moving member 9, thereby lifting the slide 4 through the hollow pressure member 7 and the height adjusting mechanism 6 into an upper limit position as shown by a chain line on the left side in FIG. 6. To prevent undue falling of the upper die 5 in the upper limit position, there is provided a falling prevention mechanism 13 on the side frame 1b at a position corresponding to the upper limit position of the slide. The falling prevention mechanism 13 is constituted of a hydraulic cylinder 13a and a piston rod 13b provided with a return spring 14. The piston rod 13b has a forward end serving as a supporting portion 13c adapted to support the bottom of the slide 4 lifted. Thus, undue falling of the movable upper die is prevented. FIG. 6 shows a twin type vulcanizer such that two sets of upper and lower dies 5 and 2 are installed in the same vulcanizer frame 1. In such a twin type vulcanizer, another falling prevention mechanism (not shown) similar to the mechanism mentioned above is provided at position A of the right side frame 1b corresponding to the location on the left side frame 1b. Reference numeral 15 designates a known central mechanism provided on the base frame 1a at the central position of the fixed lower die 2 for supplying and discharging a heating medium (steam or the like) and opening an elastic forming member formed of an elastically deformable material such as a rubber bag and adapted to contact the inner surface of the green tire set on the fixed lower die 2. Generally in such a vertical opening/closing type tire vulcanizer as mentioned above, as the movable upper die is vertically moved along the frame, the accuracy of such movement is improved as compared with the rotary opening/closing type vulcanizer, and the opening/closing mechanism is made compact. However, as the upper die 5 in its open position is located just over the lower die 2 in the frame, there is a possibility of a serious mechanical damage and a dangerous human accident occurring because of possible misoperation or pressure escape in the vertically moving member 9. Therefore, utilization of the falling prevention means is essential. Further, the falling prevention mechanism 13 as shown FIG. 6 is generally located in a sufficient space between the side frame 1b and the slide 4, and it is often used in the case where the vertical opening/closing mechanism and the clamping mechanism are different from the above-mentioned mechanism.
However, the above-mentioned slide falling prevention means has the following problem. That is, the falling prevention mechanism 13 is an essential safety mechanism in the vertical opening/closing type vulcanizer, and it is necessary to locate a pair of the falling prevention mechanisms 13 on both side frames 1b since the slide guides 3 are provided on a center frame 1d between both the side frames 1b in the twin type vulcanizer as shown in FIG. 6. Similarly in a single type vulcanizer, two falling prevention mechanisms 13 are necessary. The reason for this is that if the slide 4 were supported by a single mechanism 13, the pressure from the vertically moving member 9 would be applied to the slide guide 3 on the side frame 1b having no falling prevention mechanism, causing a damage of the guide 3. Therefore, it is always necessary to provide a plurality of falling prevention mechanisms 13 at positions equally spaced from each other and at the same exact height. This causes an increase in cost and accuracy in the installation of the mechanisms. Further, the structure of the machine is complicated so as to thus hinder the object of making the machine compact and simple.